1. Field of the Invention
This invention relates to knobs for post valves and, more specifically, to a knob which provides three methods of operating the post valve.
2. Description of the Prior Art
Pressurized gas cylinders, such as those used for medical purposes, include a post valve for controlling the flow of gas. The post valve includes a threaded end, a body, and a threaded stem. The threaded end is coupled to the compressed gas cylinder. The body is typically rectangular and includes an outlet. The stem includes a threaded portion and an exposed portion. The exposed portion includes flats shaped to be engaged by a wrench or other device. The stem threaded portion is threaded into the body and rotates to open and close the valve. Around the stem is a bonnet. The bonnet is also threaded into the body, at a different location from the stem, and prevents the stem from disconnecting with the body.
The body includes an internal passage that allows fluid communication between the threaded end and the outlet. Typically, the outlet is a passage that extends in a direction generally perpendicular to the internal passage. A landing is disposed between the internal passage and the outlet. The landing has a surface that extends in a direction generally perpendicular to the internal passage. The stem travels in a direction generally parallel to the internal passage and generally perpendicular to the outlet passage. The stem is structured to contact the landing. When the stem is contacting the landing, gas can not flow through the passage and the valve, therefore, it is closed. When the stem is spaced from the landing, the valve is open. When the stem is rotated one direction, typically counterclockwise, the stem moves away from the landing. Rotating the stem clockwise will moves towards and contacts the landing.
Thus, the valve may be opened by rotating the stem in one direction, typically counterclockwise. The valve may be closed by rotating the stem in the opposite direction, typically clockwise.
For medical applications, a compressed gas cylinder will typically utilize a yoke. The yoke includes a body having a medial opening sized to fit around the valve body, that is, a rectangular opening. The yoke also includes a T-handle screw to secure the yoke to the post valve. The yoke further includes an conduit. The yoke conduit is in fluid communication with the post value outlet. The yoke conduit includes an externally threaded attachment end that may be coupled to a hose or other device.
Early post valves included a wrench that was sized to fit flat portions on the external portion of the stem. To open or close the valve, the user placed the wrench on the stem and rotated the wrench. This design had the advantage of a top that was narrower than the valve body. Thus, the yoke could be easily installed over the post valve. The disadvantage was that the valve required an extra tool in order to open or close the valve. This design also allowed industrial users, e.g., those who filled the cylinder with the compressed gas, to use a tool, such as a modified socket wrench to open and close the valve quickly.
A second embodiment of a post valve included a winged knob that was coupled to the exposed stem. The winged knob eliminated the need for a separate tool; however, the knob made it difficult to place the yoke on the stem valve. Additionally, the size of the winged knob was limited to the size of the medial opening on the yoke. Because the size of the winged knob was limited, the knob sometimes did not provide enough leverage for older or infirm patients to operate the valve. Additionally, the winged knob prevented the industrial users from using a socket wrenches to open the valve.
Another embodiment of post valves incorporated a winged knob having an extended stem. Thus, the valve could still be opened by hand while having an exposed stem which could be turned with a wrench or a socket wrench. These valves were, however, longer than prior stem valves and cost more to manufacture. Additionally, it was still difficult to install a yoke over the winged knob.
Another type of post valve incorporated a pivoting handle. The pivoting handle was narrower than the valve body. The handle included a slotted end that straddled the stem. A pin pivotally coupled the handle to the stem. To install a yoke, a user pivoted the handle to be generally parallel to the axis of the post valve. To use the handle, the handle was pivoted to be generally perpendicular to the axis of the post valve. Thus, in one position, the handle did not interfere with installation of the yoke. In the other position, the handle provided leverage for rotating the stem. Moreover, because the handle could be aligned with the post valve, the handle could be of any length. When a longer handle was used, a greater lever arm was created making operation of the valve easier for the infirm. Because the handle is coupled to the stem, however, an industrial user cannot use a wrench to operate the valve.
There is, therefore, a need for a post valve knob that allows a yoke to be installed easily, while allowing for operation of the valve with or without a wrench, and that provides greater leverage so that the valve may be operated by the infirm.
There is a further need for such a post valve knob that can be mounted on existing post valves.
These needs, and others, are satisfied by the invention which provides a knob having an elongated body with a collapsible handle. The knob body includes a cavity extending along the axis of the body. A first end of the body includes a slot extending perpendicular to the body axis. The handle has a cross-sectional size and shape of a valve stem. The handle is structured to move between a first position and a second position. In the first position, the handle is substantially disposed within the cavity. As such, the handle extends in a direction generally parallel to the axis of the knob. In this position, a yoke may be easily installed. Additionally, the exposed end of the handle has the same general dimensions as a valve stem. Thus, the handle may be manipulated by a wrench. In the second position the handle is disposed within the first end slot. Thus, the handle extends perpendicularly to the axis of the post valve. In this position, the handle provides a lever with a sufficient length to make operation of the valve more convenient to the infirm.
Accordingly, it is an object of this invention to provide a knob for a medical post valve having a handle with two positions allowing three modes of operation. The first handle position, a retracted position, allows the knob to be turned by hand or by a wrench. With the handle in the second, extended position, the handle acts as a lever and the knob can be turned easily using the extended handle.